/Engine/Source/Runtime/Engine/Public/AudioDevice.h
Iterate over the active AudioComponents for wave instances that could be playing.Indexof first wave instance that can have a source attached
int32 GetSortedActiveWaveInstances ( [TArray](API\Runtime\Core\Containers\TArray)< [FWaveInstance](API\Runtime\Engine\FWaveInstance) * > & WaveInstances, const [ESortedActiveWaveGetType::Type](API\Runtime\Engine\ESortedActiveWaveGetType__Type) GetType )